FreeType位图为空

FreeType bitmap is empty

本文关键字：位图 FreeType      更新时间：2023-10-16

我使用freetype来显示文本，在本教程的帮助下: http://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_Text_Rendering_01

但是我看到的都是空的方块，我玩了很多着色器，得出的结论是，正方形的alpha值总是0.0，也由于某种原因，程序在第一次编译编辑的文本着色器后崩溃

代码如下:顶点着色器

#version 420
//vertexData.xy contains pos vertexData.zw contains uv coords
in vec4 vertexData;
out vec2 TexCoord;
void main(){
    gl_Position = vec4(vertexData.x, vertexData.y, 0.0, 1.0);
    TexCoord = vertexData.zw;
}

片段着色器

#version 420
in vec2 TexCoord;
out vec4 fragData;
uniform sampler2D tex;
uniform vec4 TextColor;
void main(){
    //TextColor.rgb is the color texture(tex, TexCoord).r is texture alpha value
    fragData = vec4(TextColor.rgb, texture(tex, TexCoord).r * TextColor.a);
}

FreeType的

//Freetype init and face creation is in func Font::init()
void Font::renderText(const char *text, float x, float y, float sx, float sy, float rgba[4]){
//Attribute and Uniform Locations
GLint vDataLoc = ShaderResource::TextProgram->getAttributeLocation("vertexData");
GLint textColLoc = ShaderResource::TextProgram->getUniformLocation("TextColor");
GLint texSamplerLoc = ShaderResource::TextProgram->getUniformLocation("tex");
const char *p;
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
FT_Set_Pixel_Sizes(face, 0, 48);
//iterate through text
for(p = text; *p; p++) {
    if(FT_Load_Char(face, *p, FT_LOAD_RENDER))
        continue;
    FT_GlyphSlot g = face->glyph;
    int width = to_nearest_pow2( g->bitmap.width );
    int height = to_nearest_pow2( g->bitmap.rows );
    glUniform4fv(textColLoc, 1, rgba);
    glEnable(GL_TEXTURE_2D);
    Texture Tex;
    Tex = Texture();
    Tex.bind();
    Tex.setParameter(GL_TEXTURE_WRAP_S, GL_CLAMP);
    Tex.setParameter(GL_TEXTURE_WRAP_T, GL_CLAMP);
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    //At first I thought I was passing wrong formats to glteximage2d so I played around with it using gl alpha, gl luminance alpha, gl luminance8 alpha8 etc...
    //I believe the issue is that g->bitmap.buffer was not created properly i must not be loading that char correctly??
    glTexImage2D(
        GL_TEXTURE_2D,
        0,
        GL_RED,
        width,
        height,
        0,
        GL_RED,
        GL_UNSIGNED_BYTE,
        g->bitmap.buffer
    );
    Tex.active(0);
    glUniform1i(texSamplerLoc, 0);
    //Then I create textbox and draw it using a vertex array obj and vbos using gl triangle strip etc...

Main.cpp Freetype函数调用

    //Disable Normal Shader Enable Text Shader
    mainProgram->disable();
    textProgram->use();
    //Scale x & Scale y / window get screen width and height
    float sx = 2.0 / window->getFrameBufferWidth();
    float sy = 2.0 / window->getFrameBufferHeight();
    //Text color
    float color[4] = {0.0,0.0,0.0,1.0};

    IHateComicSans.renderText("Hello World!", 0.0,   0.0, sx, sy, color);
    textProgram->disable();
    mainProgram->use();

在gltexImage2d之后，glGetError返回GL_INVALID_OPERATION，但仅在文本的最后一次迭代期间

问题是在我的纹理类，通过使用opengl函数修复。

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